The action of the "Stress Factor Ostrich (Arenales - Fauna and Flora)" was tested in the release of superoxide anion by cells in the peripheral blood of rhea (Rhea americana). Sixteen samples of 0.5mL of venous blood were collected through the jugular vein in the morning and placed in heparinized tubes. The leukocytes were separated into polymorphonuclear (PMN) and mononuclear (MN). The production of superoxide anion by phagocytes of peripheral blood was determined using the chromogen ferricytochrome C. There was a reduction of superoxide by MN cells in the presence of "Stress Factor Ostrich" indicating a positive influence of product against oxidative stress. Furthermore, future researches, such as the evaluation of other reactive oxygen intermediates and antioxidant enzymes, researches.